ISC (Instruction Set Computer) refers to a computer architecture defined by its instruction set , which is the collection of machine-level commands the processor can execute . It serves as an interface between hardware and software, dictating how software instructs the CPU to perform tasks . There are two main types of ISCs : RISC (Reduced Instruction Set Computer) , focusing on simpler , faster instructions, and CISC (Complex Instruction Set Computer), using more complex instructions to perform multiple operations per command .